C++:以编程方式初始化输入 [英] C++ : initialize input programmatically

问题描述

如果我们有这个代码片段:

If we have this code snippet:

int a;
cout << "please enter a value: "; 
cin >> a;

在终端中，输入请求看起来像这样

And in the terminal, the input request would look like this

please enter a value: _

如何以编程方式模拟用户的输入.

How can I programatically simulate a user's typing in it.

推荐答案

这里是如何使用 rdbuf() 函数，从 检索假输入std::istringstream

Here's a sample how to manipulate cin's input buffer using the rdbuf() function, to retrieve fake input from a std::istringstream

#include <iostream>
#include <sstream>
#include <string>
using namespace std;

int main() {

    istringstream iss("1 a 1 b 4 a 4 b 9");
    cin.rdbuf(iss.rdbuf());  // This line actually sets cin's input buffer
                             // to the same one as used in iss (namely the
                             // string data that was used to initialize it)
    int num = 0;
    char c;
    while(cin >> num >> c || !cin.eof()) {
        if(cin.fail()) {
            cin.clear();
            string dummy;
            cin >> dummy;
            continue;
        }
        cout << num << ", " << c << endl;
    }
    return 0;
}

看看效果

另一种选择(更接近 Joachim Pileborg 在他的评论 恕我直言)，就是把你的阅读代码放到一个单独的函数中，例如

Another option (closer to what Joachim Pileborg said in his comment IMHO), is to put your reading code into a separate function e.g.

int readIntFromStream(std::istream& input) {
    int result = 0;
    input >> result;
    return result;
}

这使您可以对测试和生产进行不同的调用，例如

This enables you to have different calls for testing and production, like

// Testing code
std::istringstream iss("42");
int value = readIntFromStream(iss);

// Production code
int value = readIntFromStream(std::cin);

这篇关于C++:以编程方式初始化输入的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！